Control for compressors



Sept. 4, 1934.

B. s. AlKMAN CONTROL FOR COMPRESSORS Filed July so, 1932 3 Sheets-Sheet '1 r m Q v I 7 m Mm I i f M 5 a N m- W 3w hm. a g b0 Wi wm m 1 mm m .0 1 0 ma l m. f w. 3 W

p 4- B. s. AIKMAN CONTROL FOR COMPRESSORS 3 Sheets-Sheet 2 Filed July 30, 1932 I A ll Ill B. S. AIKMAN CONTROL FOR COMPRESSORS Sept. 4, 1934.

Filed July 30, 1932 3 Sheets-Sheet 3 llll l| ll I w w M Patented Sept. 4, 1934 1,972,751 common FOR comasssoas Burton S. Aikman, Milwaukee, Wis., assignor to The Westinghouse Air Brake Company, Wilmerding, Pa., a corporation of Pennsylvania Application July 30, 1932, Serial No. 626,503 Claims. (01. 230-4) system. falls below a predetermined value, there-' by automatically causing unloading of the compressor in the event of failure of the lubricant l5 pump or stoppage or breakage of a conduit of the lubricant circulating system.

A further object of the invention is to provide a fluid compressor having an unloader, with a governor that is responsive to variations in pres-v sure of the fluid compressed by the compressor and to variations in pressure of the fluid lubricant in the lubricating system for effecting operation of the unloader to unloading .position when the pressure of the fluid compressed by the .25 compressor exceeds a predetermined value and when the pressure of the fluid lubricant in said system falls below a predetermined value.

A further object of the invention is to provide a governor for a fluid compressor, having the above noted characteristics, that is simple in construction and inexpensive to manufacture.

These and other objects of the invention that will be made apparent throughout the ijurther description thereof, are attained by means of the apparatus hereinafter described and illustrated in the accompanying drawings; wherein Fig. 1 is an elevational view, partially in section, disclosing a fluid compressor having governor mechanism embodying features of the invention. 7

Fig. 2 is a sectional view of the governor valve device shown in Fig.1;

Fig. 3 is an elevational view, partially in section, of a fluid compressor having a modified form of governor valve device;

Fig. 4 is a sect onal view of a governor valve device shown in Fig. 3; and

Figs. 5 and 6 are sectional views of a further modification of a governor valve device that may be applied to the compressor and unloader disclosed in Fig. 3.

Referring to the drawings, the invention is disclosed as applied to a motor driven fluid compressor of the reciprocating piston type, the compressor comprising a crank case 11 upon which moved to unloading position when the pressure,

is mounted a piston guide section 12, that is partially surrounded by an intake casing 13 containing an intake chamber 14, which receives air at atmospheric pressure through-an opening 5.

A head casing 16 is mounted upon thecasing 13 50 and which contains a compression cylinder 17 in which the piston 18 reciprocates'. The cylinder 17 is surrounded by a chamber 19 containing water which s'ervesto cool the pistoncylinderi fi The piston 18 is provided with a, ring valve 21 of a well known type,'which is mounted for longitudinal movement in a groove 22 in the upper end of the piston 18. The casing 16 is also provided with a valve chamber 23 containing a disc type outlet check valve device 24 of a well known type, which permits the compressed fluid in the piston cylinder 17 to pass through an opening 25, in the upper end of the cylinder, into the valve chamber 23 from whence it is conducted to a reservoir'56 through a pipe 60.

Air at atmospheric pressure is drawn into the piston cylinder 1'7 past the ring valve 21 from the intake chamber 14 when the piston 18 is moved downwardly, and creates suction in the cylinder 17 and is compressed within the piston 0- cylinder 1'1 upon the upstroke thereof, until the pressure within the cylinder exceeds that within the valve chamber 23 and reservoir 56,'at which time the valve device is iorced open and the compressed fluid is forced into the valve chamber and into the reservoir through the outlet passage 26. I

The casing 16 also contains an unloader device 27, which, as shown in Fig. 1, comprises a valve 28 contained within a valve chamber 29 which is open to the piston cylinder 17. The valve 28 controls communication from valve chamber 29 and the cylinder 17 to a chamber. a, 31, which is open to the atmosphere and is pro--"" vided with an operating stem 33 which extends exteriorly of the casing 16 and is guided in a threaded nut 34 which serves to close the outer end of the valve chamber 31. The valve is normally yieldingly retained in closed position by means of a spring 35 contained within a cham- 10 her 36 in the nut 34 and which is disposed between the inner end of the chamber 36 and'a collar 37 carried by the stem 33. A pin 38 in the stem 33 limits outward movement of the collar 37.

In the apparatus disclosed in Fig. 1, the unloader valve 28 is adapted to be actuated to open or unloading position by a rocking lever 39, that is adapted to operatively engage a collar 41 and a nut 42 secured to the stem 33 of the valve 28. no

The lever is adapted to oscillate upon a pivot pin 43 carried upon a bracket 44 that is secured to the exterior of the casing 16.

The lower end of the lever 39 engages a rod 45, which extends transversely through the easing 13 and is guided in a tube 46, that is secured by a fluid-tight connection to the walls of the casing 13 and to a diaphragm casing 47 that is secured exteriorly of the casing 13 and which is provided with an inwardly directed bushing 48 by means of which the casing 47 is secured to the casing 13.

The diaphragm casing 4'7 is provided with a cover 49 and a diaphragm 51 is clamped between the cover 49 and the casing 47. The diaphragm divides the space between the cover and the casing into two separate chambers 52 and 53, the former being connected to a pipe or conduit 54 which receives fluid lubricant under pressure from a fluid lubricant circulating system, having a circulating pump, not shown, driven by the crank shaft 2 of the compressor. The pumpmay be a rotary gear type pump, which comprises-a easing 3 containing the usual intermeshed pump gears and having an intake 4 beneath the level of the lubricant in the crank case 11, and an outlet pipe '7. One of the gears of the circulating pump is driven through a shaft 8 having a gear worm 9 fixed thereon, which meshes with a gear worm 20 that is fixed upon the crank shaft 2 of the compressor. Lubricant entering the intake 4, as the pump is operated by the crank shaft of the compressor, is discharged into the conduit 54, which is provided with a branch passage 30 for conducting lubricant to the moving parts of the compressor, the pump, pipe '7, branch passage 30, and the crank casing 11 constituting a lubricant circulating system. The rod is connected to a follower 55 that is secured to the diaphragm 51, so that when the diaphragm is moved toward the left, the lever 39 is rotated in a clockwise direction and forces the valve 28 to open position through engagement of the lever with the engaged by the seat ring 65.

collar 41. The chamber 31 is open to the atmosphere through a passage 40 in the nut 34 and passage 50 in the collar 37, and consequently so long as the valve remains open, the air drawn into the piston cylinder 1'7 is forced to the atmosphere instead of being compressed.

The chamber 53 on the right side of the diaphragm 51, communicates with the reservoir 56 through a pipe 5'7, the compressor governor or regulating valve device 58 and a pipe 59.

- The regulating valve device 58 is shown in Fig.2, and comprises a casing '70 containing a valve chamber 61 that is closed by a cap 62 and which contains a valve piston 63 having seat rings 64 and 65 at opposite ends thereof, the seat ring 64-being of smaller diameter than the'seat ring 65. The inner end of the chamber 61 is provided with an annular valve seat 66, disposed within'a. groove 67, and which is adapted to be engaged by the seat ring 64. The cap 62 is provided with an annular valve seat 68, disposed within a groove 69, and which is adapted to be A plunger '71, having a stem '72 which extends through a guide opening '73 in the cap 62, engages the piston valve 63, as indicated in Fig. 2, and serves to press the seat ring 64 against the seat 67. The outer end of the stem 72 is engaged by an adjustable screw '74 that is, threaded into a lever '75 that is mounted for rotation about a pin '76 carried by the cap 62, the pin '74 being locked in adjusted position by means of a lock nut '77.

The free end of the lever 75 is provided with aseries of notches '78 for receiving the loop '79 of a spring 81 that is attached to a bracket 82 integrally secured to the casing '70. The force with which the valve piston 63 is held inits lowermost position, wherein the seat ring 64 engages the valve seat 66, may be varied by moving the loop '79 of the spring 81 either toward the pivot shaft '76 or away therefrom to decrease or increase, respectively, the pressure which the spring 81 may exert upon the plunger '71 through the lever '75.

The pipe 57 opens into the chamber 61 through a port 83, which registers with an annular groove 84 in the valve piston 63, which communicates with the spaces 85 and 86 in the chamber 61 at the lower and upper ends, respectively, of the valve piston 63, through notches 80 and 87, respectively, cut in the upper and lower portions of the periphery of the valve piston. With no fluid pressure in the system, the valve piston 63 will be held seated by spring 81, so that pipe 5'7 is connected to the atmosphere through port 83, groove 84, notch 87, space 86 at the upper end of :valve piston 63, and passage 90.

prompt and positive movement of the valve pis- 1 ton to its upper seat and closing communication from the groove 84 to the atmosphere. Fluid un-- der pressure then flows from the reservoir 56 to the diaphragm chamber 53 through space 85, notch 80, groove 84, port 83, and pipe 57. 31 The pressure of the fluid in the diaphragm chamber 53 overcomes the pressure of the fluid lubricant in the diaphragm chamber 52 and causes the diaphragm 51 to be moved to the left, so as to move the rod 45 and rotate the lever for 1 opening the unloader 'valve 28. When theunloader valve is open, the compressor cannot function to compress fluid, and consequently no fluid under pressure is forced into the reservoir so long 7 as the unloader is-in unloading position. 1

to reservoir pressure when the valve piston is at its upper seated position, the reservoir pressure must fall to avalue below that at which the valve piston was moved from its lower seat before the 1 valve piston will move downwardly.

When the pressure of the fluid in the reservoir 56 falls below the said value determined by the tension of the spring 81, the spring will force the plunger 71 and valve piston 63 to its lower posi- 1 tion against the pressure of the fluid in the reservoir acting on the lower end of the valve piston, thereby shutting off the flow of fluid under pressure from the reservoir and opening the diaphragm chamber 53 to the atmosphere through 1 pipe 5'7, passage 83, annular groove 84, notch 8'7, space 86 and passage 90.

1 When the pressure on the right face of the diaphragm 51 is thus reduced, the spring 36 returns the unloader valve 28 to closed or loading posithe 'unloader valve to unloading position when the pressure of the fluid within reservoir 56 exceeds a predetermined value and will cause the unloader valve to move to loading position when the pressure of the fluid is reduced to a predetermined value.

In the event of failure of the lubricant circulating system of the compressor, such as would cause the pressure of the fluid lubricant in said circulating system and in the pipe 54 to fall below a predetermined value required for maintaining the spring 10 in compressed conditiomthe spring will force the diaphragm '51 and rod 45 to the left and cause movement of the unloader valve 28 to unloading position. Unloading of the compressor while the pressure of the fluid in the. reservoir is below that required to normally operate the unloader valve, will direct attention to the disordered condition of the lubricating system and protect the'compressor by relieving it of load while the supply of lubricant is inadequate.

Referring to the apparatus disclosed in Figs. 3 and 4, a modified form of pressure regulating device is disclosed, wherein the unloader valve isoperated by a piston subject to fluid pressure con-- trolled by the regulating valve device. For this purpose a piston 91 is provided, which is contained in a chamber 93 within a bushing 94 threaded into the casing 16. The piston 91 is connected to the valve 28 by a stem 92, and the pipe 57 is connected to the chamber at one side of the piston. The valve 28 is normally yieldingly retained in closed position by means of a spring 95 that is disposed between the inner end of the bushing 94 and the inner face of the piston 91. When the outer face of the piston 91 is subjected to the pressure of the fluid in the reservoir 56, the piston 91 is moved toward the right against the tension of the spring 95 and opens the valve 28 for the purpose of unloading the compressor, as in the device shown in Fig. 1.

The regulating valve device 58 is substantially the same as that disclosed in Figsl, with theexception that the unloading of the compressor by failure of pressure in the lubricating system is effected by relieving the tension of the spring 81 sufiiciently to permit upward movement of theof the diaphragm device 97. The diaphragm device 9'7 comprises'acasing 98 that is attached to the casing of the regulating valve device 58, by means of brackets 99 and 101. A dia-- phragm 102 is clamped between the casing 98 and the cover 103, the diaphragm dividing the I space between the casing and the cover into two separate compartments 96 and 104. A follower 105 is secured to the diaphragm 102 within the chamber 104 and which is provided with a stem determined value.

- failure of the lubricating system.

The outer end of the lever 112 is pivotallyconnected to a link 115 that is attached to the lower end of the spring 81. An extension 116 formed I During normal operation of the compressor, the

pressure of the lubricant in the lubricant circulating system of the compressor, acting on the left face of the diaphragm 102 is sufficient to maintain the diaphragmin the right hand position, wherein the adjustment screw 117 engages the lug 119 so that the desired tension is .ap-

plied to the spring 81 for maintaining the unloader valve in loading position until the pressure of the fluid within the reservoir 56 attains a prepiston 63 may readily force the valve piston 63- to its uppermost position and permit fluid to flow from the reservoir 56 through pipe 59, regulating valve device 58 and pipe 57 to the left face of the piston 91 of the unloading valve and cause opening movement thereof.

It will be apparent from the foregoing, thatthe The screw pressure of the lubricantin the lubricant, circulating system acting on the diaphragm 102 serves to alter the regulating characteristics of the regulating valve device and to cause operation of the unloader to unloading position upon In Figs. 5 and 6, a modified form of pressure regulating device is disclosed that is applicable to the form of unloader device disclosed in Fig.

3. The regulating valve device is the same as that disclosed in Fig. 4, with the exception that the spring 81, which is adjustably attached to the lever arm 75, is attached at its lower end to an adjustment screw 121, that is positioned for adjustment in a bracket 122 integrally connected to the'casing 70 of the regulating valve device 58. The screw 121 is adapted to be locked in adjusted position by means of the lock nuts 123 and 124. The lever 75 is provided with an extension 125 having a slotted eyelet 126, the purpose of which will hereinafter appear.

The pipe 54, that is connected to the lubricant circulating system of the compressor, is connected to a piston chamber 127 within a casing 128 that is closed by a threaded nut 129 to which the threaded end of the pipe 54 is connected. The

piston chamber 127 contains a piston 131 having apacking gasket 132 that is secured to the piston by means of a follower plate 133. The piston 131 is provided with a stem 134, which extends through a spring chamber 135 and projects exteriorly of the casing 128 through a guide open- "throughlthe slotted eyelet 126 in the lever extension 1125, and' which is provided with an en larged head 138 .for engaging the uppecface of culating system,'not shown, andin the pipe 54,

the Seyelet 126 for rotating the lever 75 in a counter-clockwise direction when the piston 131 is moved downwardly'by a spring 139' that is disposed'within'the spring chamber 135 and which surrounds the stem 134.

- Under normal operating conditions, the pressure of the fluid lubricant in the lubricant ciractingon the lower face of thepiston 131, com- 1 presses the spring 139 and moves the piston 131 to its uppermostposition, wherein the head 138 on the stem 137 is spaced from the eyelet 126 andpermits'iree movement of the lever TIE independently of the stem 137. When the piston 131" isin its uppermost position, the spring 81 serves to control the movement of the valve piston 63 in the manner of the devices: shown in :Figs. 1

and 3, so that fluid under pressure is supplied from the reservoir56 to the left face of the piston "91 or the unloader device, shown in Fig. 3, through pipe 57.

In the event of a failure of the lubricantcirculating system that would cause a reduction in pressure in the pistonchamber 127, the spring 139 forces the piston 131 to its lowermost position,

' wherein the follower 133 engages the annular notched stop rib 140. When the piston 131 is in it's-lowermost position, shown in Fig. 5, the head [138.on the stem 137 engages the eyelet 126 and 1 piston 63 to its uppermost position for supplying "rotates the lever 75 in a counter-clockwise direction, so that'the fluid pressure acting on the lower I end of the valve piston 63 may force the valve fluid i'rom the reservoir 56 to the left face of the piston'91 of the unloader valve device for causing it to move to unloadingposition.

' of any control 01 the fluid pressure regulating From the foregoing, it is apparent that when the pressure. of the fluid lubricant in the lubricating system falls below a value insufficient to ..maintain the piston 131in its uppermost position,

the downward movement of the piston will cause rotation 01'" the lever 75 and relieve the spring 81 valve device 58. When this occurs, the valve piston is-raised by the fluid pressure on the under race thereof and fluidunder pressure is supplied to the piston 91, thereby causing the unloader valve to move to unloading position.

7 While but three embodime'ntsof the invention are'disclosed, it is obvious that changes, omissions and additionsmay be madein the pressure regulating apparatus forzfluid compressors disclosed,

- without departing from the spirit of the invention.

, Having now described my invention, what I claim as new and desire to secureby Letters Patent, is:

1." The combination with a fluidcompressor whaving a lubricant circulating. system operated insaid system acting thereon.

pressed by said compressor acting thereon and controlledrby the pressure .of the fluid lubricant I 2. The fcombination with a fluid compressor having 'anunloading device and a fluidlubricant ulatingthe pressure Iot the fluid compressed by circulating system, ofan unloader device ior'regthe compressor and responsive to variations in the pressure of the fluid compressed by the compressor'acting thereon and to variationsfof the pressure of .the'fluidlubricant in said system actdevice.

3. The combination with a fluid compressor having a normally closed fluid pressureactuated unloading device actuated to unloading position by fluid under pressure, and a fluid lubricant circulating system operated by the compressor for supplying fluid lubricant under pressure to moving parts of the compressor, of a fluid pressure regulating device for regulating thev pressure of the fluid compressed by the compressor and responsive to variations in the pressure of fluid compressed by the compressor and to variations in the pressure of the fluid lubricant under pressure in said system and adapted either upon a predetermined increase in pressure of said compressed fluid or a decrease in pressure of the fluid lubricant acting on said regulating device, to supply fluid under pressure to said unloading device for moving it to unloading position.

4. The combination with a fluid compressor having an unloading device and a fluid lubricant circulating system operated by the compressor for supplying fluid lubricant under pressure to moving parts of the compressor, of a device for regu- 1 lating the. pressure of fluid compressed by the compressor and operated by fluid under pressure compressed by the compressor and including means for operating saidunloading device, and means subject to fluidlubricantunden pressure 1 for varying the iregulating characteristics oi said regulating device.

5. The combination-with a fluid compressor having an unloader and a .fluid lubricant circulating system, of a means actuated by fluid 1 under pressure compressed by the compressor to actuate the unloader to unload the compressor and subject to pressure of thelubricant in said system, and means whereby fluid lubricant under pressure in said system acting on said means 1 controls the operation of said means to eiiect actuation of said unloader when the pressure of the fluid lubricant in the system falls below a predetermined value.

6. The combination with a fluid compressor 1 having an unloader and a fluid lubricant cireulating system, of means adapted to hold the unloader in unloading position, and means actuated by fluid lubricant under pressure in said system for rendering said means ineffective to hold said 5 .culating system, of means adapted to hold the unloader in unloading position, means actuated by fluid lubricant under pressure in said system 1 for rendering said means ineffective to hold said unloader in unloading position when the pressure of the, fluid in said system exceeds a predetermined value, and means subject to the pressure or the fluid compressed by-the com- 1 pressor for rendering the second said means inefiective to render theflrst said means ineffective. 8. The combination with a fluid compressor having'an unloader and a fluid lubricant circulating system, of means adapted to hold the unloader in unloading position, means actuated by fluid lubricant under pressure in said system for rendering said means ineffective to hold said .unloader in unloading position when the pressure of the fluid in said system exceeds a predetermined value, means subject to the pressure of fluid compressed bythe compressor for rendering the second said means ineffective to render the first said means ineffective, andmeans for controlling the delivery of fluid compressed by the compressor-to the means subject to the pressure of fluid compressed by the compressor.

9. The combination with a fluidcompressor having an unloader and a fluid lubricant circulating system, of means adoptedto hold the unloader in unloading position; means actuated by fluid lubricant under pressure insaid system forrendering said means ineffective to hold said unloaderin unloading position when the pressure of the fluid in said system exceeds a predetermined value, means subject to the pressure of fluid compressed by the compressor for rendering the second said means lnefiective to render the first said means inefiectiva'and means responsive to variations in the pressure of the fluid compressed by the compressor for controlling the delivery of fluid compressed by the compressor to the means subject to the pressure of fluid compressed by the compressor.

10. The combination with a fluid compressor having an unloader and a fluid lubricant circulating system, of means for actuating the unloader comprising a movable abutment subject on one side to the fluid lubricant under pressure in said system and on the other side to a spring adapted to move said abutment for effecting actuation of the unloader when the pressure of the fluid in said system falls below a predetermined value, the other side of said abutment being subject to fluid compressed by'the compressor whereby the abutment is moved to actuate the unloader against the pressure of the fluid in said system acting on said abutment.

11. The combination with a fluid compressor having an unloader and a fluid lubricant circulating system, of a movable abutment subject on one side to fluid under pressure, means operable upon a variation in the pressure of the fluid compressed by the compressor for controlling the supply of fluid under pressure to said abutment, and means subject to the pressure of the fluid lubricant in said system for controlling said means. I

12. The combination with a fluid compressor having an unloader and a fluid lubricant circulating system, of means actuated by fluid, under pressure for actuating said unloader, means responsive to variations in the pressure-of the fluid compressed by the compressor for controlling the supply of fluid under pressure to said fluid actuated means, and means responsive to variations in the pressure of the fluid lubricant in said system for controlling the second said means. I

13. The combination with a fluid compressor having an unloader and a fluid lubricant circulating system, of means actuated by fluid under pressure {or actuating said unloader, valve means responsive to variation in the pressure '01 the fluid compressed by the'compressor for controlling the supplyof fluid under pressure to' said fluid actuated means, adapted upon a predetermined increase in said fluid pressure to supply fluid under pressure to said fluid actuated means for effecting movement of said unloader to unloading position, and upon a predetermined decrease in said fluid pressure to eflect movement of said unloader to loading position, means for regulating said valve means so as to vary the variations in fluid pressure necessary to efiect pressure for actuating. said unloader, lvalve means responsive to variations in the pressure of the fluid compressed by the compressor for i'controllin'g the supply of fluid under pressure to said fluid actuated means, adapted upon a pre-.

determinedaincrease in said fluid pressure to supply fluid under pressure to said fluid actuatedmeans for effectingmovement of said unloader.

to unloading position, and upon a predetermined decrease in said fluid pressure to'efiectmovement of saidunloader to loading position, adjustable means for regulating said valve means so as to vary the variationsjin fluid pressure necessary to effect its operation, and means responsive to variations in the pressure of the fluid lubricant in said system for controlling said regulating means. v

-15. The combination with a fluid compressor having an unloader and a fluid lubricant circulating system, of means actuated byfluid under pressure for actuating said unloader, valve means responsive to variations in the pressure of the fluid compressed by the compressor for controlling the supply of fluid under pressure to said fluid actuated means, adapted upon a predetermined increase in said fluid pressure to supply fluid under pressure to said fluid actuated means for eflectin'g movement of said unloader to unvary the variations in fluid pressure necessary to effect its operation, and a movable abutment subject to the pressure of the fluid lubricant in said system for altering the adjustment of said regulating means.

is, The combination with a fluid compressor having an unloader and a fluid lubricant circu-' lating system, of means actuated by fluid'under pressure for actuating the unloader, means for" controlling the delivery. of fluid under pressure to said actuating means responsive to variations of the pressure of the fluid compressed by the compressor,-.means for. regulating the -control-.

ling meansgfor determining the variations .in the pressure required to effect operation of said "controlling means, and means operable by fluid lubricant. under pressure in said system adapted when the pressure of the fluid in the system falls below a predetermined amount to so affect the regulating means as to eifect operation of said controlling means.

v 17. The combination with a fluid compressor having .anunloader and a fluid lubricantcirculating system, of means actuated by fluid under pressure for actuating the unloader, means for controlling the delivery of fluid under pressure to saidactuating means responsive to variations of the pressure of the fluid compressed by the compressor, adjustable spring means for regulating the controlling means fordetermining the variations in the pressure required to eilect operation of .said controlling means, and means including a movable abutment subjected to fluid under pressure in said system for controlling said regulating spring adapted to be rendered ineffective to control said regulating spring means when the pressure of the fluid in said system is above a predetermined amount and to be effective to control said spring means when the pressure in said system falls below a predetermined-value.

18. The combination with a fluid compressor having an unloading device, and a fluid lubricant circulating system operated by the compressor for supplying fluid lubricant under pressure to moving parts of the compressor, of a device for regulating the pressure of fluid compressed by the compressor and operated by fluid under pressure compressed by the compressor for effecting operation of the unloading device, and means actuated by fluid lubricant under pressure supplied from said system for varying the regulating characteristics of said regulating device.

19. The combination with a fluid compressor having a fluid lubricant circulating system operated by the compressor for supplying fluid lubricant under pressure to moving parts of the compressor, of means for regulating the pressure of the fluid compressed by the compressor including an unloader, said means being responsive to variations in pressure of the fluid compressed by the compressor and to the pressure of the fluid lubricant in said system for effecting operation of the unloader.

20. Compressor mechanism comprising a fluid compressor, a fluid pressure actuated unloading valve device for said compressor, a fluid lubricant circulating system operated by the compressor for delivering fluid lubricant under pressure to moving parts of the compressor, a regulating valve device actuated by fluid compressed by said compressor for controllingthe actuating fluid acting on said unloading valve device, and means actuated by fluid lubricant under pressure in said circulating system for maintaining said regulating valve eifective for controlling said unloading valve device and for so affecting said regulating-valve device that the unloader is moved to open position upon a predetermined reduction in the fluid lubricant pressure acting on said means.

21. The combination with a fluid compressor having a fluid pressure actuated unloading valve device and a fluid pressure actuated valve device responsive to variations in pressure of fluid compressed by the compressor for controlling the fluid under pressure supplied to said unloading valve device, and a fluid lubricant circulating system operated by the compressor for delivering fluid lubricant under pressure to moving parts of the compressor, of means. adapted to be maintained in a position by fluid lubricant in said system for rendering said regulating means effective to '7 control said unloading valve device so long as the delivery of said compressed fluid to said means,

fluid pressure in said system is above a predetermined value and to cause the regulating valve device to operate to eflect actuation ofsaid unloading valve device when the fluid pressure in the system falls below a predetermined value.

22. The combination with a fluid compressor having a pressure lubricating system, of means operating upon a predetermined increase in the pressure of fluid compressed by the compressor for unloading the compressor and means operating upon a reduction in the pressure of lubricant in the lubricating system to a predetermined degree for also efiecting the operation of said unloading means to unload the compressor.

23. The combination with a fluid compressor having an unloader and a fluid lubricant circulating system, of means actuated by fluid under pressure for actuating said unloader, valve means responsive to variations in the pressure of the fluid compressed by the compressor for-controlling the supply of fluid under pressure to said fluid actuated means, adapted upon a predetermined increase in 'said fluid pressure to supply fluid under pressure to said fluid actuated means for efiecting movement of said unloader to un- 100 leading position, and upon a predetermined decrease in said fluid pressure to effect movement of said unloader to loading position, an adjust- .able spring for regulating said valve means so as to vary the variations/in fluid pressure necessary to effect its operation, and a movable abutment subject to the pressure of the fluid lubricant in said system for altering the adjustment of said regulating spring. I 24. The combination with a fluid compressor having an unloader and a fluid lubricant circulating system, of means actuated by the fluid under pressure compressed by the compressor for actuating the unloader, means for controlling the and means whereby fluid under pressure in said system acting on the first said means controls the operation of the first said means.

25; The combination with afluid compressor having an unloader and a fluid lubricant circu- 3 lating system, of means actuated by the fluid under pressure compressed by the compressor for actuating the unloader, means for controlling the delivery of said compressed fluid to said means, and means whereby fluid lubricant under pressure in said system acting on the first said means controls the operation of the first said means to eflect actuation of the unloader whenthe pressure 01' the fluid lubricant in the system falls below a predetermined value. 9

BURTON S. AIKNLAN. 

